The present invention relates to circuitry for isolating a detachable external device from electronic equipment containing the signal processing circuitry for the external device.
Current consumer electronic equipment often is expandable by the consumer. For example, current receivers for direct satellite television systems (DSS) include plugs into which infrared (IR) remote control receivers and transmitters may be plugged. The external IR remote control receiver connection permits a user to place a television in one room and the satellite receiver in another room, and still allow the user to control the satellite receiver using an IR remote control unit. The external IR remote control transmitter permits the satellite receiver to control an external device, such as a VCR, which is responsive to IR remote control signals, all in a known manner.
However, whenever an external unit is connected by a wire to electronic equipment, it is possible to create ground loops, which results in distortion and possible malfunction of the equipment. It is further possible that an electrostatic charge present in the external device will discharge through the electronic equipment when the external device is plugged in, thus, damaging the electronic equipment. It is also possible for the wire connecting the external device to the electronic equipment to emit electromagnetic interference (EMI), which can affect external equipment. In addition, in consumer electronic equipment it is possible that the external device plugged into the plug will be the wrong device, or that it will be configured incorrectly. For all of these reasons, it is desirable to provide circuitry in electronic equipment which includes a slug for external devices to electrically isolate the external device from the electronic equipment, to isolate potential electrostatic discharge (ESD) damage from the electronic equipment, and to minimize EMI emissions.
In accordance with principles of the present invention, an electronic system, including a connector for an external device, includes a signal processor, responsive to the external device and an electrical isolation device, coupled between the external device connector and the signal processor. Such a system can further include electromagnetic interference suppression circuitry coupled between the external device connector and the electrical isolation device. Such a system can also further include electrostatic discharge suppression circuitry coupled between the external device connector and the electrical isolation device.